Single frequency low power RFID device

ABSTRACT

Methods, systems, and apparatuses for a reader transceiver circuit are described. The reader transceiver circuit incorporates a frequency generator, such as a surface acoustic wave (SAW) oscillator. A reader incorporating the reader transceiver circuit is configured to read a tag at very close range, including while being in contact with the tag. The transceiver can be coupled to various host devices in a variety of ways, including being located in a RFID reader (e.g., mobile or fixed position), a computing device, a barcode reader, etc. The transceiver can be located in an RFID module that is attachable to a host device, can be configured in the host device, or can be configured to communicate with the host device over a distance. The RFID module may include one or more antennas, such as a first antenna configured to receive a magnetic field component of an electromagnetic wave and a second antenna configured to receive an electric field component of an electromagnetic wave. The RFID module may include a detector that is configured to determine if the RFID module is positioned in proximity to an object, such as a RFID tag. The detector may operate as a trigger for the RFID module, to enable or trigger a function of the RFID module.

The present application claims the benefit of U.S. Appl. No. 60/784,450,filed Mar. 22, 2006, which is incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to radio frequency identification (RFID)technology, and in particular, to improved RFID readers.

2. Background Art

Radio frequency identification (RFID) tags are electronic devices thatmay be affixed to items whose presence is to be detected and/ormonitored. The presence of an RFID tag, and therefore the presence ofthe item to which the tag is affixed, may be checked and monitoredwirelessly by devices known as “readers.” Readers typically have one ormore antennas transmitting radio frequency signals to which tagsrespond. Because the reader “interrogates” RFID tags, and receivessignals back from the tags in response to the interrogation, the readeris sometimes termed as “reader interrogator” or simply “interrogator.”

With the maturation of RFID technology, efficient communication betweentags and interrogators has become a key enabler in supply chainmanagement, especially in manufacturing, shipping, and retailindustries, as well as in building security installations, healthcarefacilities, libraries, airports, warehouses etc.

Current RFID systems suffer from various problems. For example, RFIDreaders suffer from high costs associated with programmable frequencysynthesizers, power amplifiers, and high-speed high-resolutiondigitizers. However, these and other similar electronic devices arenecessary to meet governmental regulatory requirements, such as FCC part15.247, when designing high performance RFID systems.

Furthermore, if two or more tags and their associated boxes are presentwithin the interrogation space, readers have difficulty distinguishingone tag from another within that interrogation space. For example, iftwo boxes and their associated tags were present, the interrogator wouldread the presence of both tags, but specifically determining which boxwas which is difficult unless one of the boxes is removed to besingulated.

Mobile readers have disadvantages. Readers require relatively largeamounts of power to operate, which tends to limit battery life of mobileRFID terminals. Furthermore, readers produce excessive heat when housedin confined spaces such as mobile terminals. Still further, mobile RFIDsystems require large, bulky antennas to perform far field reads, toenable interrogation at long ranges.

RFID readers and tags are normally very susceptible to interference fromother RFID readers in the general area. For example, readertransmissions normally interfere with other readers in the nearbygeneral area. Readers transmitting at full power can even adverselyaffect the host system by which they are controlled and in which theyare housed. When writing to RFID tags, the need for an interference freeenvironment is paramount. Often this requires interference free zones tobe configured, so that tags in the interference free zones can bereliably written.

Thus, what is needed are ways to improve a quality of communicationsbetween readers and tags in an RFID communications environment.

BRIEF SUMMARY OF THE INVENTION

Methods, systems, and apparatuses for improved RFID readers aredescribed herein. In an aspect, a SAW oscillator is used to provide highfrequency oscillating signals for a reader, enabling a very compactreader design. In another aspect, a near field antenna is used in areader to enhance short range reads of tags. In a still further aspect,a reader circuit is mounted on a flexible substrate, to enablepositioning of the reader circuit in a variety of locations.

In an aspect of the present invention, a radio frequency identification(RFID) reader transceiver is described. The transceiver includes afrequency generator, such as a surface acoustic wave (SAW) oscillator,an amplifier, a directional coupler, an antenna, and a demodulator. Thefrequency generator generates a radio frequency (RF) signal that ismodulated with an input data stream, to generate a modulated RF signal.The amplifier receives the modulated RF signal and outputs an amplifiedmodulated RF signal. The directional coupler has a first port thatreceives the amplified modulated RF signal. The antenna is coupled to asecond port of the directional coupler. The demodulator is coupled to areverse port of the directional coupler. The demodulator receives a tagresponse signal from the antenna through the directional coupler, andoutputs a baseband signal.

In another aspect of the present invention, a method for a transceiverin a radio frequency identification (RFID) reader is described. An inputdata signal modulates a radio frequency (RF) oscillating signalgenerated by a frequency generator to generate a modulated RF signal.The modulated RF signal is amplified to generate an amplified modulatedRF signal. The amplified modulated RF signal is transmitted. A tagresponse signal is received. The tag response signal is demodulated intoa baseband signal.

In an aspect, the amplified modulated RF signal is radiated as a nearfield RF signal. In a further aspect, an antenna of the reader iscontacted with a tag when transmitting the amplified modulated RF signalto the tag. In an alternative aspect, the an antenna of the reader ismoved near, but not in contact with the tag, when transmitting theamplified modulated RF signal to the tag.

In aspect of the present invention, a RFID transceiver can be coupled tovarious host devices in a variety of ways, including being located in aRFID reader (e.g., mobile or fixed position), a computing device, abarcode reader, etc. The RFID transceiver can be located in an RFIDmodule that is attachable to a host device, can be configured in thehost device, or can be configured to communicate with the host deviceover a distance.

In an example aspect, a radio frequency identification (RFID)communication system includes a host computer and an RFID module coupledto the host computer. The RFID module includes a transceiver, a protocolprocessor configured to process RFID tag data, a host interfaceconnector module configured to communicate RFID tag data with thecomputer, a plurality of antennas, and an antenna selector to couple anantenna of the plurality of antennas to the transceiver.

In a further aspect, the plurality of antennas includes a first antennaconfigured to receive a magnetic field component of an electromagneticwave and a second antenna configured to receive an electric fieldcomponent of an electromagnetic wave.

In another aspect, the plurality of antennas includes an antennaconfigured to be more efficient at radiating a communication signal intothe near field region than into the far field region. For example, in anaspect, the antenna is a near field E-field coupling antenna, a nearfield H-field inductive coupling loop antenna, or a lossy transmissionline.

In another aspect, an antenna is configurable to match properties of anantenna of a RFID tag proximate to the RFID module. For example, theantenna may be configured to be tuned by contacting the antenna with aRFID tag, such as due to a loading capacitance of the RFID tag.

In another aspect, a RFID module includes a detector that is configuredto determine if the RFID module is positioned in proximity to an object,such as a RFID tag. The detector may operate as a trigger for the RFIDmodule, to enable or trigger a function of the RFID module. For example,a transceiver of the RFID module may be enabled if the detectordetermines that the RFID module is positioned in proximity to a RFIDtag.

For example, a RFID module may include first and second antennas, and aswitch coupled to the first antenna and the second antenna. A detectoris coupled to the switch. The switch is configured to enable one of thefirst antenna or the second antenna according to the detector.

In another example, a tuning module is configured to tune an antenna ofthe RFID module if a detector of the RFID module indicates that theantenna is proximate to an object.

In another example, the transceiver may perform communications using asubstantially constant frequency or using frequency hopping, dependingon whether the detector detects an object.

In example aspects, the detector may include a pressure sensor, acapacitive sensor, an optical sensor, an interrupter switch, a proximitysensor, and/or other type of sensor.

In another aspect, a RFID module includes a barcode reader interface.The barcode reader interface includes an interface circuit configured toexchange information with a host system. For instance, the barcodereader interface may be configured to transmit tag data to the hostsystem in a signal format that emulates a signal format generated by abarcode reader.

These and other objects, advantages and features will become readilyapparent in view of the following detailed description of the invention.Note that the Summary and Abstract sections may set forth one or more,but not all exemplary embodiments of the present invention ascontemplated by the inventor(s).

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIG. 1 shows an environment where RFID readers communicate with anexemplary population of RFID tags.

FIG. 2 shows a block diagram of receiver and transmitter portions of aRFID reader.

FIG. 3 shows a plan view of an example radio frequency identification(RFID) tag.

FIG. 4 shows an example reader transceiver circuit, according to anembodiment of the present invention.

FIG. 5 shows a more detailed circuit diagram of the reader transceivercircuit of FIG. 4, including an application specific integrated circuit(ASIC), according to an example embodiment of the present invention.

FIGS. 6 and 7 show example steps for a reader transceiver, according toembodiments of the present invention.

FIG. 8 shows output waveform signals for an example barcode scanner andan example reader transceiver circuit, according to an embodiment of thepresent invention.

FIG. 9 shows a block diagram of a conventional RFID reader.

FIG. 10 shows a block diagram of an example RFID reader, according to anembodiment of the present invention.

FIGS. 11A and 11B show a block diagram of a host computer coupled to aRFID module, according to an example embodiment of the present invention

FIG. 11C shows example embodiments of the present invention asattachable accessories for example mobile handheld devices.

FIG. 12 shows an example reader transceiver circuit, according to anembodiment of the present invention.

FIG. 13 shows the reader transceiver circuit of FIG. 12 on a flexiblesubstrate, according to embodiment of the present invention.

FIGS. 14-19 show example RFID communication systems, according toembodiments of the present invention.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit(s) of a reference number identifies the drawing in which thereference number first appears.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

Methods, systems, and apparatuses for RFID devices are described herein.In particular, methods, systems, and apparatuses for improved readersystems are described.

The present specification discloses one or more embodiments thatincorporate the features of the invention. The disclosed embodiment(s)merely exemplify the invention. The scope of the invention is notlimited to the disclosed embodiment(s). The invention is defined by theclaims appended hereto.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

Furthermore, it should be understood that spatial descriptions (e.g.,“above,” “below,” “up,” “left,” “right,” “down,” “top,” “bottom,”“vertical,” “horizontal,” etc.) used herein are for purposes ofillustration only, and that practical implementations of the structuresdescribed herein can be spatially arranged in any orientation or manner.Likewise, particular bit values of “0” or “1” (and representativevoltage values) are used in illustrative examples provided herein torepresent data for purposes of illustration only. Data described hereincan be represented by either bit value (and by alternative voltagevalues), and embodiments described herein can be configured to operateon either bit value (and any representative voltage value), as would beunderstood by persons skilled in the relevant art(s).

Example RFID System

Before describing embodiments of the present invention in detail, it ishelpful to describe an example RFID communications environment in whichthe invention may be implemented. FIG. 1 illustrates an environment 100where RFID tag readers 104 communicate with an exemplary population 120of RFID tags 102. As shown in FIG. 1, the population 120 of tagsincludes seven tags 102 a-102 g. A population 120 may include any numberof tags 102.

Environment 100 includes any number of one or more readers 104. Forexample, environment 100 includes a first reader 104 a and a secondreader 104 b. Readers 104 a and/or 104 b may be requested by an externalapplication to address the population of tags 120. Alternatively, reader104 a and/or reader 104 b may have internal logic that initiatescommunication, or may have a trigger mechanism that an operator of areader 104 uses to initiate communication. Readers 104 a and 104 b mayalso communicate with each other in a reader network.

As shown in FIG. 1, reader 104 a transmits an interrogation signal 110 ahaving a carrier frequency to the population of tags 120. Reader 104 btransmits an interrogation signal 110 b having a carrier frequency tothe population of tags 120. Readers 104 a and 104 b typically operate inone or more of the frequency bands allotted for this type of RFcommunication. For example, frequency bands of 902-928 MHz and2400-2483.5 MHz have been allowed for certain RFID applications by theFederal Communication Commission (FCC).

Various types of tags 102 may be present in tag population 120 thattransmit one or more response signals 112 to an interrogating reader104, including by alternatively reflecting and absorbing portions ofsignal 110 according to a time-based pattern or frequency. Thistechnique for alternatively absorbing and reflecting signal 110 isreferred to herein as backscatter modulation. Readers 104 a and 104 breceive and obtain data from response signals 112, such as anidentification number of the responding tag 102. In the embodimentsdescribed herein, a reader may be capable of communicating with tags 102according to any suitable communication protocol, including EPC Class 0,Class 1, Gen 2, and other binary traversal protocols and slotted alohaprotocols, any other protocols mentioned elsewhere herein, and futurecommunication protocols.

FIG. 2 shows a block diagram of an example RFID reader 104. Reader 104includes one or more antennas 202, a receiver and transmitter portion220 (also referred to as transceiver 220), a baseband processor 212, anda network interface 216. These components of reader 104 may includesoftware, hardware, and/or firmware, or any combination thereof, forperforming their functions.

Baseband processor 212 and network interface 216 are optionally presentin reader 104. Baseband processor 212 may be present in reader 104, ormay be located remote from reader 104. For example, in an embodiment,network interface 216 may be present in reader 104, to communicatebetween transceiver portion 220 and a remote server that includesbaseband processor 212. When baseband processor 212 is present in reader104, network interface 216 may be optionally present to communicatebetween baseband processor 212 and a remote server. In anotherembodiment, network interface 216 is not present in reader 104.

In an embodiment, reader 104 includes network interface 216 to interfacereader 104 with a communications network 218. As shown in FIG. 2,baseband processor 212 and network interface 216 communicate with eachother via a communication link 222. Network interface 216 is used toprovide an interrogation request 210 to transceiver portion 220(optionally through baseband processor 212), which may be received froma remote server coupled to communications network 218. Basebandprocessor 212 optionally processes the data of interrogation request 210prior to being sent to transceiver portion 220. Transceiver 220transmits the interrogation request via antenna 202.

Reader 104 has at least one antenna 202 for communicating with tags 102and/or other readers 104. Antenna(s) 202 may be any type of readerantenna known to persons skilled in the relevant art(s), including adipole, loop, Yagi-Uda, slot, or patch antenna type. For description ofan example antenna suitable for reader 104, refer to U.S. Ser. No.11/265,143, filed Nov. 3, 2005, titled “Low Return Loss Rugged RFIDAntenna,” now pending, which is incorporated by reference herein in itsentirety.

Transceiver 220 receives a tag response via antenna 202. Transceiver 220outputs a decoded data signal 214 generated from the tag response.Network interface 216 is used to transmit decoded data signal 214received from transceiver portion 220 (optionally through basebandprocessor 212) to a remote server coupled to communications network 218.Baseband processor 212 optionally processes the data of decoded datasignal 214 prior to being sent over communications network 218.

In embodiments, network interface 216 enables a wired and/or wirelessconnection with communications network 218. For example, networkinterface 216 may enable a wireless local area network (WLAN) link(including a IEEE 802.11 WLAN standard link), a BLUETOOTH link, and/orother types of wireless communication links. Communications network 218may be a local area network (LAN), a wide area network (WAN) (e.g., theInternet), and/or a personal area network (PAN).

In embodiments, a variety of mechanisms may be used to initiate aninterrogation request by reader 104. For example, an interrogationrequest may be initiated by a remote computer system/server thatcommunicates with reader 104 over communications network 218.Alternatively, reader 104 may include a finger-trigger mechanism, akeyboard, a graphical user interface (GUI), and/or a voice activatedmechanism with which a user of reader 104 may interact to initiate aninterrogation by reader 104. As described further below, in anembodiment where a reader is contacted with a tag to be read by thereader, a pressure or capacitance sensor mounted on the antenna or theantenna housing may be used to trigger the reader.

In the example of FIG. 2, transceiver portion 220 includes a RFfront-end 204, a demodulator/decoder 206, and a modulator/encoder 208.These components of transceiver 220 may include software, hardware,and/or firmware, or any combination thereof, for performing theirfunctions. Example description of these components is provided asfollows.

Modulator/encoder 208 receives interrogation request 210, and is coupledto an input of RF front-end 204. Modulator/encoder 208 encodesinterrogation request 210 into a signal format, such as one ofpulse-interval encoding (PIE), FMO, or Miller encoding formats,modulates the encoded signal, and outputs the modulated encodedinterrogation signal to RF front-end 204.

RF front-end 204 may include one or more antenna matching elements,amplifiers, filters, an echo-cancellation unit, a down-converter, and/oran up-converter. RF front-end 204 receives a modulated encodedinterrogation signal from modulator/encoder 208, up-converts (ifnecessary) the interrogation signal, and transmits the interrogationsignal to antenna 202 to be radiated. Furthermore, RF front-end 204receives a tag response signal through antenna 202 and down-converts (ifnecessary) the response signal to a frequency range amenable to furthersignal processing.

Demodulator/decoder 206 is coupled to an output of RF front-end 204,receiving a modulated tag response signal from RF front-end 204. In anEPC Gen 2 protocol environment, for example, the received modulated tagresponse signal may have been modulated according to amplitude shiftkeying (ASK) or phase shift keying (PSK) modulation techniques.Demodulator/decoder 206 demodulates the tag response signal. Forexample, the tag response signal may include backscattered dataformatted according to FMO or Miller encoding formats in an EPC Gen 2embodiment. Demodulator/decoder 206 outputs decoded data signal 214.

The configuration of transceiver 220 shown in FIG. 2 is provided forpurposes of illustration, and is not intended to be limiting.Transceiver 220 may be configured in numerous ways to modulate,transmit, receive, and demodulate RFID communication signals, as wouldbe known to persons skilled in the relevant art(s).

The present invention is applicable to any type of RFID tag. FIG. 3shows a plan view of an example radio frequency identification (RFID)tag 102. Tag 102 includes a substrate 302, an antenna 304, and anintegrated circuit (IC) 306. Antenna 304 is formed on a surface ofsubstrate 302. Antenna 304 may include any number of one, two, or moreseparate antennas of any suitable antenna type, including dipole, loop,slot, or patch antenna type. IC 306 includes one or more integratedcircuit chips/dies, and can include other electronic circuitry. IC 306is attached to substrate 302, and is coupled to antenna 304. IC 306 maybe attached to substrate 302 in a recessed and/or non-recessed location.

IC 306 controls operation of tag 102, and transmits signals to, andreceives signals from RFID readers using antenna 304. In the example ofFIG. 3, IC 306 includes a memory 308, a control logic 310, a charge pump312, a demodulator 314, and a modulator 316. An input of charge pump312, an input of demodulator 314, and an output of modulator 316 arecoupled to antenna 304 by antenna signal 328.

Memory 308 is typically a non-volatile memory, but can alternatively bea volatile memory, such as a DRAM. Memory 308 stores data, including anidentification number 318. Identification number 318 typically is aunique identifier (at least in a local environment) for tag 102. Forinstance, when tag 102 is interrogated by a reader (e.g., receivesinterrogation signal 110 shown in FIG. 1), tag 102 may respond withidentification number 318 to identify itself. Identification number 318may be used by a computer system to associate tag 102 with itsparticular associated object/item/container.

Demodulator 314 is coupled to antenna 304 by antenna signal 328.Demodulator 314 demodulates a radio frequency communication signal(e.g., interrogation signal 110) on antenna signal 328 received from areader by antenna 304. Control logic 310 receives demodulated data ofthe radio frequency communication signal from demodulator 314 on inputsignal 322. Control logic 310 controls the operation of RFID tag 102,based on internal logic, the information received from demodulator 314,and the contents of memory 308. For example, control logic 310 accessesmemory 308 via a bus 320 to determine whether tag 102 is to transmit alogical “1” or a logical “0” (of identification number 318) in responseto a reader interrogation. Control logic 310 outputs data to betransmitted to a reader (e.g., response signal 112) onto an outputsignal 324. Control logic 310 may include software, firmware, and/orhardware, or any combination thereof. For example, control logic 310 mayinclude digital circuitry, such as logic gates, and may be configured asa state machine in an embodiment.

Modulator 316 is coupled to antenna 304 by antenna signal 328, andreceives output signal 324 from control logic 310. Modulator 316modulates data of output signal 324 (e.g., one or more bits ofidentification number 318) onto a radio frequency signal (e.g., acarrier signal transmitted by reader 104) received via antenna 304. Themodulated radio frequency signal is response signal 112, which isreceived by reader 104. In an embodiment, modulator 316 includes aswitch, such as a single pole, single throw (SPST) switch. The switchchanges the return loss of antenna 304. The return loss may be changedin any of a variety of ways. For example, the RF voltage at antenna 304when the switch is in an “on” state may be set lower than the RF voltageat antenna 304 when the switch is in an “off” state by a predeterminedpercentage (e.g., 30 percent). This may be accomplished by any of avariety of methods known to persons skilled in the relevant art(s).

Charge pump 312 (or other type of power generation module) is coupled toantenna 304 by antenna signal 328. Charge pump 312 receives a radiofrequency communication signal (e.g., a carrier signal transmitted byreader 104) from antenna 304, and generates a direct current (DC)voltage level that is output on tag power signal 326. Tag power signal326 is used to power circuits of IC die 306, including control logic320.

Charge pump 312 rectifies the radio frequency communication signal ofantenna signal 328 to create a voltage level. Furthermore, charge pump312 increases the created voltage level to a level sufficient to powercircuits of IC die 306. Charge pump 312 may also include a regulator tostabilize the voltage of tag power signal 326. Charge pump 312 may beconfigured in any suitable way known to persons skilled in the relevantart(s). For description of an example charge pump applicable to tag 102,refer to U.S. Pat. No. 6,734,797, titled “Identification Tag UtilizingCharge Pumps for Voltage Supply Generation and Data Recovery,” which isincorporated by reference herein in its entirety. Alternative circuitsfor generating power in a tag, as would be known to persons skilled inthe relevant art(s), may be present. Further description of charge pump312 is provided below.

It will be recognized by persons skilled in the relevant art(s) that tag102 may include any number of modulators, demodulators, charge pumps,and antennas. Tag 102 may additionally include further elements,including an impedance matching network and/or other circuitry.Furthermore, although tag 102 is shown in FIG. 3 as a passive tag, tag102 may alternatively be an active tag (e.g., powered by battery).

Embodiments of an improved RFID reader device are described in furtherdetail below. Such embodiments have advantages over conventionalreaders. Such embodiments may interact with the tags described above,other tag types, and/or may be used in alternative environments.Furthermore, the embodiments described herein may be adapted andmodified, as would be apparent to persons skilled in the relevantart(s).

EXAMPLE EMBODIMENTS

Embodiments are described herein for improved readers. These embodimentscan be implemented anywhere that readers and tags are used. For example,embodiments can be implemented in a commercial or industrialenvironment, such as in a warehouse, a factory, a business, or store,and in a military or other non-commercial environment.

In embodiment, transceivers are described that are suitable for RFIDreader devices. The transceivers are very compact, and thus can be fitinto small form factors. For example, in one embodiment, a transceiveris incorporated into a RFID module that is an attachable accessory for ahost computer, such as a mobile handheld computer.

In embodiments, various types of oscillators can be used to generate acarrier frequency for the transceiver. In example transceivers describedbelow, a surface acoustic wave (SAW) device is described as generating acarrier frequency for a transceiver, and in some embodiments alsoperforms a modulating function. Such a SAW device can be formed in asmall form factor, and thus enables a small form factor transceiver.Furthermore, a SAW device requires very low power to operate, and thusenables very low power operation for a transceiver. However, inalternative embodiments, other types of oscillator and modulatorcircuits may be used.

FIG. 4 shows an example reader transceiver circuit 400, according to anembodiment of the present invention. As shown in FIG. 4, readertransceiver circuit 400 includes a transmitter portion 450, whichincludes an oscillator 402, a surface acoustic wave (SAW) device 404, anamplifier 406, a forward power leveling controller 408, and a first(forward coupled) diode 410. Reader transceiver circuit 400 furtherincludes a receiver portion 460, which includes a second (reversecoupled) diode 412, an amplifier 414, a comparator 416, and a referencevoltage source 418. Reader transceiver circuit 400 further includes adirectional coupler 420 and an antenna 422, which are part of both thereceiver and transmitter portions 450 and 460.

In the transmit side, as shown in FIG. 4, oscillator 402 and SAW device404 form a SAW oscillator 470, as would be known to persons skilled inthe relevant art(s). SAW oscillator 470 generates an oscillating signalthat oscillates at a radio frequency. SAW oscillator 470 receives aninput data signal 424, and amplitude modulates input data of input datasignal 424 onto the radio frequency of the oscillating signal, togenerate a modulated RF signal 426.

Amplifier 406 is a radio frequency amplifier. Modulated RF signal 426 isamplified by amplifier 406. Amplifier 406 outputs amplified modulated RFsignal 428.

Directional coupler 420 may be a conventional directional coupler, aswould be known to persons skilled in the relevant art(s). Directionalcoupler 420 has four ports (first-fourth ports 452, 454, 456, and 458).First and second ports 452 and 454 of directional coupler 420 areconnected together by a through line of directional coupler 420. Thirdand fourth ports 456 and 458 of directional coupler 420 are connectedtogether by a second signal line of directional coupler 420. Third andfourth ports 456 and 458 are directional ports. Fourth port 458 is areverse port, coupling signals from second port 454 (at antenna 422).Third port 456 is a forward port, coupling signals from first port 452.

Amplified modulated RF signal 428 enters first port 452 of directionalcoupler 420, passing through directional coupler 420 to second port 454of directional coupler 420. Antenna 422 is coupled to second port 454 ofdirectional coupler 420. Antenna 422 radiates amplified modulated RFsignal 428 as transmitted RF signal 430. Transmitted RF signal 430 istransmitted to communicate with tags, including to interrogate tags andprovide tags with commands, and may also be used to provide energy topassive tags. Passive tags use the provided energy to power themselves(e.g., with a charge pump).

First diode 410 and forward power leveling controller 408 provideforward coupling, and form a feedback path used to monitor power outputand maintain an amplitude of transmitted RF signal 430 at a desiredlevel. An input of first diode 410 is coupled to third port 456 ofdirectional coupler 420. First diode 410 converts a radio frequencycarrier received on a signal 432 from third port 456 of directionalcoupler 420 to a DC level. A signal 434 output by first diode 410 isreceived by forward power leveling controller 408. In an exampleembodiment, forward power leveling controller 408 compares signal 434against a standard level. In embodiments, forward power levelingcontroller 408 outputs a feedback error signal 436. Feedback errorsignal 436 is received at SAW oscillator 470, and is used to alter anamplitude of modulated RF signal 426 output by SAW oscillator 470.

On the receive side, antenna 422 receives a tag response signal 438 froma tag, that is modulated with tag response data. Tag response signal 438enters second port 454 of directional coupler 420 from antenna 422. Aninput of second diode 412 is coupled to fourth port 458 of directionalcoupler 420. Second diode 412 receives a radio frequency carriermodulated with tag data received on a signal 440 from fourth port 458 ofdirectional coupler 420, demodulates signal 440, and outputs a basebandsignal 442. Baseband signal 442 includes tag response data.

Amplifier 414 is a baseband amplifier. Amplifier 414 amplifies basebandsignal 442, and outputs an amplified baseband signal 444.

Comparator 416 receives amplified baseband signal 444. Comparator 416compares amplified baseband signal 444 with a reference signal output byreference voltage source 418, and outputs an output data signal 446. Forexample, comparator 416 may be used to more substantially “square” or“digitize” the waveform of amplified baseband signal 444. Output datasignal 446 includes tag data, which may be further processed downstreamfrom reader transceiver circuit 400.

The components of reader transceiver 400 may have various parameters andform factors, as desired for a particular application, as would be knownto persons skilled in the relevant art(s). For example, FIG. 5 shows anexample circuit chip implementation of the reader transceiver circuit ofFIG. 4, according to an example embodiment of the present invention.FIG. 5 shows a reader transceiver circuit 500. In FIG. 5, oscillator402, amplifier 406, forward power leveling controller 408, first diode410, second diode 412, amplifier 414, comparator 416, and referencevoltage source 418 are implemented in an integrated circuit (IC) 502,which may be an application specific integrated circuit (ASIC), forexample. A power signal 504 (e.g., 3.3V or other suitable voltage) isreceived at a power port 506 of IC 502. A ground signal 508 is receivedat a ground port 510 of IC 502.

SAW device 404 is coupled between first and second ports 512 and 514 ofIC 502, which couple SAW device 404 with oscillator 402. SAW device 404may be any type of SAW resonant material, as would be known to personsskilled in the relevant art(s). For example, SAW device 404 may be aformed from a resonant material having any size, including a size lessthan a square centimeter. Oscillator 402 of IC 502 may be any type ofoscillator circuit suitable for interfacing with a SAW resonator, aswould be known to persons skilled in the relevant arts. For example,oscillator 402 may be a transistor based oscillator.

Directional coupler 420 is coupled to IC die 502 at first, second, andthird ports 516, 518, and 520 of IC 502.

Data input signal 424 is received at a data input port 522 of IC 502.Data output signal 446 is output from data output port 524 of IC 502.

Reader transceiver circuits 400 or 500 can be incorporated in devices,mobile or stationary, to read tags in a near field fashion, such as in a“contact” or nearby fashion. For example, a reader device incorporatingcircuit 400 or 500 can be moved into contact with a tag (e.g., movingantenna 422 in contact with an antenna of the tag) to read the tag, orcan be moved very close to the tag (e.g., within inches or feet) to readthe tag. Such reader devices have many advantages.

FIG. 6 shows a flowchart 600 providing example steps for operation of areader transceiver, such as circuits 400 and 500, according to anembodiment of the present invention. Other structural and operationalembodiments will be apparent to persons skilled in the relevant art(s)based on the following discussion.

Flowchart 600 begins with step 602. In step 602, an input data signal ismodulated with a radio frequency (RF) oscillating signal generated by asurface acoustic wave (SAW) oscillator to generate a modulated RFsignal. For example, in an embodiment, the SAW oscillator is SAWoscillator 470. SAW oscillator 470 generates a RF oscillating signalthat is modulated with input data signal 424 to generate modulated RFsignal 426.

In step 604, the modulated RF signal is amplified to generate anamplified modulated RF signal. For example, in an embodiment, as shownin FIG. 4, modulated RF signal 426 is amplified by amplifier 406 togenerate amplified modulated RF signal 428.

In step 606, the amplified modulated RF signal is transmitted. Forexample, in an embodiment, as shown in FIG. 4, amplified modulated RFsignal 428 is coupled to antenna 422 by directional coupler 420, andtransmitted by antenna 422 as transmitted RF signal 430.

In step 608, a tag response signal is received. For example, as shown inFIG. 4, antenna 422 receives tag response signal 438.

In step 610, the tag response signal is demodulated to a basebandsignal. For example, in an embodiment, as shown in FIG. 4, tag responsesignal 438 is coupled to diode 412 by directional coupler 420. Diode 412demodulates tag response signal 438 to baseband signal 442.Alternatively, tag response signal 438 can be demodulated in ways otherthan by diode 412, including by a quadrature mixer and oscillator, powerdetector, and by other types of demodulators.

In an embodiment, step 606 can include the step of radiating theamplified modulated RF signal from a near field radiator element. Forexample, in an embodiment, antenna 422 can be a near field radiatorelement, such as a near field E-field coupling device or a near fieldinductive coupling loop.

In an embodiment, step 606 can further include contacting a tag with thenear field radiator element. For example, antenna 422 can be actuallycontacted to a tag desired to be read, such as by contacting the antennaof the tag, when transmitting signal 428. Alternatively, antenna 422 canbe moved near to the tag desired to be read when transmitting signal428.

In embodiments, flowchart 600 can include further steps, such as shownin FIG. 7. For example, in an embodiment, flowchart 600 may furtherinclude step 702. In step 702, the amplified baseband signal is comparedto a reference voltage to generate a tag data signal. For example,comparator 416 may be used to perform step 702, to digitize signalamplified baseband signal 444. Alternatively, signal 444 may bedigitized in other ways, including by an A/D converter or a data slicer.

Flowchart 600 may include step 704. In step 704, the amplified modulatedRF signal is coupled to the SAW oscillator through a forward powerleveling control module. For example, in an embodiment, step 704 may beperformed by forward power leveling control 408. Alternatively, otherfeedback mechanisms may be used to control output power.

Flowchart 600 may include further steps and/or alternative steps, aswould be apparent to persons skilled in the relevant art(s) from theteachings herein.

In the example of FIG. 5, the effective radiated power (−6 dBi of theantenna driven multiplied by +5 dBm from the power amplifier) is 1 dBm.This is an EIRP (equivalent isotropically radiated power) level at whichthe FCC no longer requires frequency hopping per FCC 15.249(a) (50mV/M). Thus, this implementation allows a very low cost, singlefrequency SAW oscillator to be used, eliminating an expensivesynthesizer and crystal combination used in higher power conventionalimplementations. Additionally a high power (e.g., 1 Watt) amplifierrequired in conventional implementations is eliminated in theembodiments of FIGS. 4 and 5, due to the substantially lower RF powerrequirements of near field and contact interrogations of RFID tags.

Conventional RFID interrogators strive to interrogate the highest volumeof space allowable by the FCC. This results in the largest amount ofRFID tags being interrogated at one time as possible. However, thisleads to an inherent difficulty in determining which tag is which amongthe interrogated tag population. By limiting the read range to contactonly, or to contact and very short range (e.g, in the range of inches),the uncertainty of volumetric interrogations is eliminated.

By limiting the amount of power required to a level needed tointerrogate tags at contact ranges, the amount of DC power required togenerate the RF signals for near field contact reading are two to threeorders of magnitude lower than that used in a far field high powervolumetric interrogation. This results in a substantial energy savingswhen operating from battery powered sources. This further results insubstantial reductions of generated heat when enclosed within a mobilehandheld terminal.

By limiting an effective radiated power to an amount required tointerrogate at contact ranges, the radiating antenna (e.g., antenna 422)can be made very small, with a corresponding reduction in antenna gain.This allows the antenna size to be reduced from a bulky 4″ to 6″ squarepatch or linear radiator to as little as a 0.7 inch square patch, orother small size. Such an antenna can act as a near field E-fieldcoupling device, although it could also be a near field inductivecoupling loop. This antenna has the tendency to radiate very little intothe far field, but when placed in close proximity or contact with anRFID tag, will give up substantially more energy to the RFID tag throughthe near field coupling mechanism, enabling accurate reads. Atraditional low gain reduced size far field antenna may also beemployed. Either floating or ground reference antenna designs may beimplemented.

By limiting an effective radiated power to an amount required tointerrogate at only contact ranges, the radiating antenna can be madevery small, with a corresponding reduction in antenna gain. This reducesthe amount of RF susceptibility for the present reader to otherinterfering readers. Furthermore, this reduces the amount of RFinterference that the present reader presents to other readers. Stillfurther, any undesired interaction with other circuitry housed withinthe mobile terminal in minimized (when the present reader is housed in amobile terminal).

In an embodiment, by placing the present reader in close proximity to anRFID tag being read, the tag being read becomes detuned by the presenceof the present reader antenna. It therefore becomes much harder for aninterfering reader to jam the interrogation and/or writing process ofthe present reader.

FIG. 8 shows a first plot 810 of an output waveform signal 800 for anexample reader transceiver circuit and a second plot 820 of an outputwaveform signal 802 for an example barcode scanner. For example, outputwaveform signal 800 may be output data signal 446 shown in FIG. 4, for aClass 1 tag or other tag type. Output waveform signal 802 may be asimilar output data signal from a barcode scanner, such as data from aread Code 39 barcode, or other barcode type. As shown in FIG. 8, outputwaveform signals 800 and 802 are very similar in shape, and amplitude.Because of the substantial similarity of output waveform signals 800 and802, output waveform signals 800 and 802 can be received and processedby the same signal processing circuit. Thus, reader transceiver circuits400 and 500 can be incorporated in existing barcode scanner devices,including mobile barcode scanners, with the pre-existing components ofthe barcode scanner devices that process scanned barcode data being usedto process tag data, with little or no modification. Thus, embodimentsof the present invention can easily be integrated into barcode scanners.

Communication ranges for conventional RFID readers vary. For example,one conventional reader that is a long range mobile reader may have arange between 0-10 feet. Another conventional reader that is a mid-rangemobile reader, may have a range between 0-4 feet. In an embodiment, areader that is a short range mobile reader may have a range of 0-3inches, although, other ranges are also possible, depending on theparticular implementation.

In an example embodiment, a reader including features described abovemay be configured as a limited functionality reader, although this isnot required. The reader may be configured for short range, to read asingle tag at a time, and thus does not suffer from environmentscontaining multiple readers. The reader may use analog signal processingthat leverages a barcode reader's baseband circuitry.

In an embodiment, a reader as described herein can be made at very lowcost (e.g., <$20 in parts) and can operate at low power (e.g., 100 ma@5Vpeak). This is because of the very low range and very power efficientcomponents utilized by the readers described herein, such as a SAWoscillator, lower power amplifiers, etc. Furthermore, the lowerbroadcast power enables passing FCC requirements without the need forfrequency hopping, high power RF, and expensive spectral mask controls.

Still further, as described above, the present reader may be configuredto share scanner electronics, and thus can be easily incorporated intoscanner devices, such as bar code scanners and other machine readablesymbol scanner devices.

In an embodiment, the present reader is configured to use a “near-field”antenna configuration, such as described above, or including patch,linear, or loop antenna configuration. Another near-field antennaexample is a lossy transmission line type antenna (such as shown in FIG.12). The lossy line antenna is a printed circuit transmission line thatis terminated into the characteristic impedance of the transmissionline. When nothing disturbs the transmission line, it contains nearlyall RF energy within the printed structures, and terminates all energyinto the load at the end of the transmission line. In this non-disturbedmode, the lossy transmission line radiates very little energy into thefar field. Thereby allowing a stronger drive level to be injected intothe transmission line. When a disturbing element is brought within thenear field of the lossy transmission line, the characteristic impedanceis changed which causes the transmission line to give up RF energy tothe disturbing element, i.e. the RFID tag being interrogated.

Because of the mainly near-field characteristics in reader embodiments,single RFID tags can be read, which is very difficult with long-rangehandheld type readers in the presence of more then one RFID tag.

Furthermore, due to the shorter range of transmitted signals, there isless portal interference. For example, an embodiment may have aninterference range of a few meters, while a conventional reader may havean interference range as much as a mile or more.

In an embodiment, signal processing is performed in the reader. Inanother embodiment, signal processing can be performed in a host ratherthan in a mobile reader. For example, packet processing and protocol canbe handled on a host processor (e.g., much like an undecoded ScanEngine). Furthermore, digital (DBP—digital bar pattern) or analog (e.g.,SURF technology) interfaces are enabled.

FIG. 9 shows a block diagram of a conventional RFID reader 900. Reader900 is similar to reader 104 of FIG. 2, with some modifications. Forexample, a quadrature modulator 902 is shown for modulator/encoder 208,and a quadrature demodulator 904 is shown for demodulator/decoder 206.Furthermore, baseband processor 212 is shown as an FPGA (fieldprogrammable gate array)-based baseband processor 906. A protocolprocessor 908 is coupled to baseband processor 906 for protocol-levelprocessing. Protocol processor 908 is further coupled to a host, whichmay be a remote computer system, etc., by a wired or wireless link 910.

In a transmitter portion 940 of reader 900, a pair of digital-to-analogconverters (DACs) 912 a and 912 b receive first and second input datasignals from baseband processor 906. The first and second input datasignals contain information to be transmitted by reader 900, such as inan interrogation signal. DACs 912 a and 912 b output first and secondanalog signals. The analog signals are filtered by band pass filter(BPF) 916, which outputs first and second filtered analog signals thatare received by quadrature modulator 902. Quadrature modulator 902modulates the first and second filtered analog signals in a quadraturemanner with an oscillating signal 934, to output a modulated signal,which is amplified by amplifier 918. The amplified modulated signal ispassed through directional coupler 920 to antenna 922, which istypically a high-gain antenna.

In a receiver portion 950 of reader 900, antenna 922 receives a signal(e.g., from one or more tags). Directional coupler 920 couples thereceived signal from antenna 922 to an amplifier 924. Amplifier 924amplifies the received signal, and outputs an amplified received signal.The amplified received signal is received by quadrature demodulator 904,which demodulates the amplified received signal according to oscillatingsignal 934, and outputs first and second demodulated signals. The firstand second demodulated signals are filtered by a BPF 926, and first andsecond filtered demodulated signal output by BPF 926 are received by apair of digital converters (ADCs) 928 a and 928 b. ADCs 928 a and 928 bconvert the first and second filtered demodulated signals to digitalform, outputting first and second digital signals that are received bybaseband processor 906.

A phase lock loop (PLL) 930 is coupled to an output of an oscillator 932to generate an oscillating signal 934, which may contain a range ofradio frequencies used by quadrature modulator and demodulator 902 and904, and by baseband processor 906.

FIG. 10 shows a block diagram of an example RFID reader 1000, accordingto an embodiment of the present invention. The architecture of RFIDreader 1000 is simpler and requires fewer components than conventionalreader 900 of FIG. 9. A host 1002 is coupled to a reader transceivercircuit 1050. Host 1002, which may be a computer system, for example,may be internal or external to reader 1000. Reader transceiver circuit1050 includes a SAW oscillator 1010, an amplifier 1014, a directionalcoupler 1018, an antenna 1020, a power detector 1028, a band pass filter(BPF) and baseband amplifier 1032, and a data slicer 1036.

In the embodiment of FIG. 10, host 1002 outputs an input data signal1004. Input data signal 1004 is received by the SAW oscillator 1010. SAWoscillator 1010 amplitude modulates a generated RF oscillation, andoutputs a modulated radio frequency (RF) signal 1012. Modulated RFsignal 1012 is received by amplifier 1014, which outputs an amplifiedmodulated RF signal 1016. Directional coupler 1018 receives amplifiedmodulated RF signal 1016, and outputs amplified modulated RF signal 1016to antenna 1020. Antenna 1020 transmits RF transmitted signal 1022.

Antenna 1020 receives tag response signal 1024, which is coupled onto asignal 1026 by directional coupler 1018. Signal 1026 is a modulated RFsignal. Power detector 1028 receives signal 1026, and outputs a basebandsignal 1030. Baseband signal 1030 of power detector 1028 is received byBPF 1032. BPF 1032 outputs filtered baseband signal 1034. Data slicer1036 receives filtered baseband signal 1034, and outputs an output datasignal 1038. Host 1002 receives output data signal 1038.

As is apparent by comparing readers 900 and 1000 of FIGS. 9 and 10,reader 900 is a simpler architecture than that of reader 1000.Furthermore, reader 900 can be implemented in a much smaller formfactor, requires fewer components, less power, and has further benefits.For example, instead of the complex PLL 930 and oscillator 932combination as used in reader 900, reader 1000 uses a fixed frequencySAW oscillator 1010. Furthermore, antenna 1020 is a near field or farfield antenna, as opposed to antenna 922, which is typically a high gainfar field antenna. Thus, antenna 1020 enables near field reads of tags,with reduced interference.

Thus, as shown in FIG. 10, transceiver embodiments of the presentinvention may be interfaced with a host, such as a host computer, toreceive input data signals from the host for transmission, and to outputreceived data signals to the host. Transceiver embodiments of thepresent invention may be incorporated in RFID modules that interfacewith hosts. For example, FIG. 11A shows a host computer 1152 that iscoupled to an RFID module 1154 by a communication link 1156.Communication link 1156 may be a wired link (e.g., a cable) or awireless link (e.g., BLUETOOTH or 802.11).

Host computer 1152 and RFID module 1154 may be coupled together over adistance or may be directly coupled to each other. For example, FIG. 11Bshows RFID module 1154 attached to host computer 1152 as an attachableaccessory. In the example of FIG. 11B, host computer 1152 is containedin a first housing, and RFID module 1154 is contained in a secondhousing. The first and second housings are attached to each other, andexchange signals through communication link 1156. The first and secondhousings may be attached by coupling mechanisms, mounts, etc., as wouldbe known to persons skilled in the relevant art(s). In an embodiment,host computer 1152 may be a hand-carried, mobile device. In such anembodiment, RFID module 1154 may provide RFID functionality to hostcomputer 1152. Examples of mobile versions of host computer 1152 includea laptop computer, a personal digital assistant (PDA), a BLACKBERRY orTREO device, a barcode reader, a cell phone, or other handheld device.

FIG. 11C shows example embodiments of the present invention asattachable RFID accessories, for example mobile haudheld devices. Thesmall form factor enabled by embodiments of the present invention allowthe implementation of embodiments as attachable accessories. Forexample, FIG. 11C shows a reader transceiver module 1102 as a RFIDmodule that is attachable to each of several mobile devices. The mobiledevices shown are a universal wireless handheld device 1104, an NGphaser device 1106, an MC50 enterprise digital assistant 1108, an MC1000handheld computer 1110, an MC3000 mobile computer 1112, and an MC70enterprise digital assistant 1114, each distributed by SymbolTechnologies, Inc., of Holtsville, NY.

Reader transceiver module 1102 is a housing that encloses a readertransceiver circuit, such as one of circuits 400, 500, or 1050. Thehousing of reader transceiver module 1102 is configured to be attachableto a mobile device at an interface of the mobile device, such as anoption port. For example, the housing of reader transceiver module 1102connects directly into a recessed port of device 1104, device 1106, andhandheld computer 1110. The housing of reader transceiver module 1102attaches to digital assistant 1108, mobile computer 1112, and digitalassistant 1114 via interface modules 1116, 1118, and 1120, respectively.Interface modules 1116, 1118, and 1120 have housings that each have arecessed first pod for attaching the housing of reader transceivermodule 1102, and a second port that conforms to the respective mobiledevice (e.g., to an interface of the mobile device). Thus, in each case,reader transceiver module 1102 can be attached to each mobile device ina conforming manner for better form factor.

FIG. 12 shows an example reader transceiver circuit 1202, according toan embodiment of the present invention. Reader transceiver circuit 1202is shown as an ASIC 1208, and is similar to reader transceiver circuit400 of FIG. 4, except that a lossy transmission line 1204, which may bea strip line on a flex substrate, is used as an antenna. Furthermore, atransmit side feedback loop is not present, and a mixer 1206 is used onthe receive side to remove a radio frequency carrier from a received tagresponse signal (instead of a diode such as diode 412 shown in FIG. 4).

Radio transceiver circuit 1202 includes ASIC 1208, a SAW device 1212,lossy transmission line 1204, and a termination 1210. ASIC 1208 includesmixer 1206, an amplifier 1214, a directional coupler 1216, a comparator1218, and a reference voltage source 1220. A power signal 1250 (e.g.,3.3V or other suitable voltage) is received at a power port of ASIC1208. A ground signal 1252 is received at a ground port of ASIC 1208.

In the transmit side, as shown in FIG. 12, SAW device 1212 receives aninput data signal 1222, and amplitude modulates input data of input datasignal 1222 onto a radio frequency oscillating signal, to generate amodulated RF signal 1224.

Amplifier 1214 is a radio frequency amplifier. Modulated RF signal 1224is amplified by amplifier 1214. Amplifier 1214 outputs amplifiedmodulated RF signal 1226.

Directional coupler 1216 has four ports (first-fourth ports 1230, 1232,1234, and 1236). First and second ports 1230 and 1232 of directionalcoupler 1216 are connected together by a through line of directionalcoupler 1216. Third and fourth ports 1234 and 1236 of directionalcoupler 1216 are connected together by a second signal line ofdirectional coupler 1216. Third and fourth ports 1234 and 1236 aredirectional ports. Fourth port 1236 is a reverse port, viewing signalsfrom second port 1232. Third port 1234 is a forward port, viewingsignals from first port 1230.

Amplified modulated RF signal 1226 enters first port 1230 of directionalcoupler 1216, passing through directional coupler 1216 to second port1232 of directional coupler 1226. A first end of lossy transmission line1204 is coupled to second port 1232 of directional coupler 1216. Asecond end of lossy transmission line 1204 is coupled to termination1210. Lossy transmission line 1204 normally radiates very little energyuntil it is disturbed by a conductor or dielectric in close proximity,as in the case of a RFID tag in close proximity. It then gives upenergy, by radiating amplified modulated RF signal 1226 as a transmittedRF signal to communicate with tags, including to interrogate tags andprovide tags with commands, and may also be used to provide energy tags.Tags use the provided energy to power the tags (e.g., with a chargepump). Transmission line 1204 is an efficient radiator in the near fieldregion.

On the receive side, lossy transmission line 1204 receives a tagresponse signal from a tag, that is modulated with tag response data.The tag response signal enters second port 1232 of directional coupler1216 from lossy transmission line 1204. Mixer 1206 is coupled betweenthird and fourth ports 1234 and 1236 of directional coupler 1216. Mixer1206 mixes a radio frequency carrier modulated with tag data received ona signal 1240 from fourth port 1236 (coupled from second port 1232) ofdirectional coupler 1216, with an RF oscillating signal 1242 from thirdport 1234 (coupled from first port 1230), to demodulate signal 1240, andoutputs a baseband signal 1244. Baseband signal 1244 includes tagresponse data.

Comparator 1218 receives baseband signal 1244. Comparator 1218 comparesbaseband signal 1244 with a reference signal output by reference voltagesource 1220, and outputs an output data signal 1246. For example,comparator 1218 may be used to more substantially “square” the waveformof baseband signal 1244. Output data signal 1246 includes tag data,which may be further processed downstream from reader transceivercircuit 1202.

Elements of reader transceiver circuit 1202 can have a variety ofparameter values. For instance, in an example embodiment, SAW oscillator1212 may generate a 915 MHz fixed oscillating frequency. Amplifier 1214may have a 16 dB gain. Directional coupler 1216 may be a 16 dB coupler.These parameter values are provided for illustrative purposes, and arenot intended to be limiting.

FIG. 13 shows a flexible substrate 1302 that may be used to mount readertransceiver circuit 1202. Flexible substrate 1302 is made from aflexible material, such as a plastic, polymer, or other substratematerial that flexes. Because substrate 1302 flexes, and can thus beshaped, flexible substrate 1302 enables circuit 1202 to be positioned inand on objects, such as mobile devices, in a variety of configurations.Furthermore, flexible substrate 1302 may have an adhesive backing, sothat radio transceiver circuit 1202 can be easily attached to an outsidesurface or an inside surface.

Embodiments of the present invention may be implemented in a variety ofapparatuses and form factors. For example, reader transceiver circuits,such as circuits 400, 500, 1050, and 1202 can be implemented in avariety of devices to provide reader functionality. For example, readertransceiver circuits can be implemented in a mobile reader, a stationaryreaders, a watch, a glove, a URA device, a phone (e.g., a cell phone),and a wearable mobile device. Furthermore, the reader transceivercircuits described above, including circuits 400, 500, 1050, and 1202,can be combined in any manner.

Example System Embodiments

As described above, embodiments of the present invention can beimplemented in many forms, including in RFID readers, in attachable RFIDmodule accessories, in barcode readers, in mobile devices, and in otherdevices. Some further example system implementations are describedbelow. These embodiments may be adapted, modified, and combined in anymanner, as would be apparent to persons skilled in the relevant art(s).

For instance, FIG. 14 shows a RFID communication system 1400, accordingto an example embodiment of the present invention. As shown in FIG. 14,system 1400 includes a host computer 1402 and a RFID module 1404. RFIDmodule 1404 includes RFID functionality for communicating with RFIDtags. RFID module 1404 may be implemented in a reader, in an RFIDmodule, or other device. Host computer 1402 may be computer system,similar to host 1002 described above. Host computer 1402 may beimplemented in a desktop computer, server, mobile handheld computer(e.g., a PDA), a barcode scanner (e.g., handheld), a cell phone, orother device described elsewhere herein or otherwise known.

Host computer 1402 and RFID module 1404 communicate over communicationlink 1406. Communication link 1406 may be a wired link (e.g., a cable)or a wireless link (e.g., BLUETOOTH or 802.11), similar to communicationlink 1156 described above, for example. Similarly to host computer 1152and RFID module 1154 described above with respect to FIG. 11, hostcomputer 1402 and RFID module 1404 may be coupled directly together(e.g., RFID module 1404 may be an attachable accessory) or may bedevices that operate separately and communicate over a distance.

As shown in the embodiment of FIG. 14, RFID module 1404 includes a hostinterface connector 1408, protocol processor 1410, transceiver 1412, anantenna interface 1414, and an antenna system 1416. Host interfaceconnector 1408 is configured to enable RFID module 1404 to exchange datawith host computer 1402 over communication link 1406. Host interfaceconnector 1408 may be configured to exchange data according to anysuitable protocol, proprietary or industry standard, including thosedescribed elsewhere herein, or otherwise known. In an embodiment, hostinterface connector 1408 may be configured similarly to networkinterface 216 described above with respect to FIG. 2. Host interfaceconnector 1408 may include hardware (e.g., electrical circuits),software, firmware, or any combination thereof, to perform itsfunctions.

Protocol processor 1410 is configured to perform protocol levelprocessing for data received from host interface connector 1408 to beprovided to transceiver 1412, and for tag data received from transceiver1412. For example, protocol processor 1410 may provide processing (suchas formatting) of data according to RFID protocols such as EPC Class 0,Class 1, Gen 2, etc. Protocol processor 1410 may include hardware,software, firmware, or any combination thereof, to perform itsfunctions.

Transceiver 1412 receives a data signal from protocol processor 1410,modulates a carrier frequency with the data signal, and provides themodulated signal to antenna system 1416 through antenna interface 1414.Transceiver 1412 further receives a tag response signal from antennasystem 1416 through antenna interface 1414, demodulates the tag responsesignal, and provides the demodulated signal to protocol processor 1410.In embodiments, transceiver 1412 can be configured according to any ofthe transceivers described herein, including being configured similarlyto circuits 400, 500, 1050, and 1202, and including any combination ofmodifications of the same.

Antenna interface 1414 provides a signal interface between antennasystem 1416 and transceiver 1412. For example, in an embodiment, antennainterface 1414 includes a cable, such as a coaxial cable, and/or one ormore transmission lines. In further embodiments, such as described inmore detail below, antenna interface 1414 may include furtherfunctionality, such as providing an antenna selection function when morethan one antenna is present in antenna system 1416.

Antenna system 1416 includes one or more antennas for transmitting RFcommunications signals, such as RF communication signal 1418, and forreceiving RF communications signals. For example, RF communicationsignal 1418 may be a tag read or interrogation signal. Received RFcommunication signals may be tag responses, for example.

Antenna system 1416 can include any of a variety of types of antenna,including those described elsewhere herein or otherwise known. Forexample, in an embodiment, antenna system 1416 may include a magneticfield (“H-field”) sensitive antenna type (e.g., a loop antenna), anelectric field (“E-field”) sensitive antenna type (e.g., a dipoleantenna), and/or antennas configured to be more sensitive in the nearfield region (e.g., a patch, a near field E-field coupling device, anear field H-field inductive coupling loop, a lossy transmission line,etc.) or far field region.

FIG. 15 shows a RFID communication system 1500, according to anotherexample embodiment of the present invention. As shown in FIG. 15, system1500 is configured generally similarly to system 1400 shown in FIG. 14,with a RFID module 1520 shown in place of RFID module 1402. RFID module1520 is generally similar to RFID module 1402, with antenna system 1416including a first antenna 1504 and a second antenna 1506. Furthermore,antenna interface 1414 is shown as an antenna selector 1502.

In an embodiment, first antenna 1504 and second antenna 1506 areconfigured identically. In another embodiment, first antenna 1504 andsecond antenna 1506 are configured differently. For example, in anembodiment, first antenna 1504 may be a magnetic field sensitive antennatype, such as a loop antenna, and second antenna 1506 may be an electricfield sensitive antenna type, such as a dipole antenna. In this manner,RFID module 1520 includes different types of antennas for differentcommunication environments. For example, second antenna 1506 may beconfigured to radiate a radio frequency (RF) signal 1510 receivable byRFID tags in a near field region. First antenna 1504 may be configuredto radiate a RF signal 1508 receivable by RFID tags in a far fieldregion.

Antenna selector 1502 is coupled between transceiver 1412 and first andsecond antennas 1504 and 1506. Antenna selector 1502 enablescommunication between transceiver 1412 and one of first and secondantennas 1504 and 1506, depending on which of first and second antennas1504 and 1506 is desired to be active in a particular situation. Antennaselector 1502 can electronically select one of antennas 1504 and 1506according to a command from host computer 1402 (e.g., input or triggeredby a user of host computer 1402), or by other mechanism. For example,FIG. 16 shows a RFID communication system 1600 configured generallysimilarly to system 1500 shown in FIG. 15, where a RFID module 1602includes a detector 1604 coupled to antenna selector 1502. Detector 1604functions as a trigger (e.g., a trigger module) that can be used toswitch first antenna 1504 from being active to second antenna 1506 beingactive, or to switch second antenna 1506 from being active to firstantenna 1504 being active.

For example, in an embodiment, detector 1604 includes a sensor todetermine whether RFID module 1602 is positioned adjacent to, or incontact with, an object. In such an embodiment, the sensor may bepressure sensor, an optical sensor, an interrupter switch, a proximitysensor, or other suitable type of sensor. In an embodiment, the sensormay be specifically configured to determine whether RFID module 1702 ispositioned in contact with a RFID tag. For example, the sensor may be acapacitive sensor, that senses a change is capacitance when detector1604 is near or contacted with a tag antenna.

In such embodiments, detector 1604 outputs a detector output signal 1606to indicate that an object (e.g., a tag) is positioned adjacent to or incontact with detector 1604. Signal 1606 is received by antenna selector1502. In an embodiment, if detector output signal 1606 does not indicatethat an object is positioned adjacent to or in contact with detector1604 (e.g., detector 1604 is not triggered), antenna selector 1502enables (e.g., passes a signal from) first antenna 1504, and disables(e.g., does not pass a signal from) second antenna 1506. If detectoroutput signal 1606 does indicate that an object is positioned adjacentto or in contact with detector 1604 (e.g., detector 1604 is triggered),antenna selector 1502 disables first antenna 1504, and enables secondantenna 1506. In such an embodiment, first antenna 1504 may beconfigured to be more efficient at far field reads while second antenna1506 is configured to be more efficient at near field reads.

FIG. 17 shows a RFID communication system 1700, according to anotherexample embodiment of the present invention. As shown in FIG. 17, system1700 is configured generally similarly to system 1400 shown in FIG. 14,with a RFID module 1702 shown in place of RFID module 1402. RFID module1702 is generally similar to RFID module 1402, with a detector 1704coupled to transceiver 1412. Detector 1704 outputs a detector outputsignal 1706 to indicate that an object (such as a tag) is positionedadjacent to or in contact with detector 1704. Detector output signal1706 is received by transceiver 1412. In an embodiment, if detectoroutput signal 1706 does not indicate that an object is positionedadjacent to or in contact with detector 1704, transceiver 1412 isdisabled. If detector output signal 1706 does indicate that an object ispositioned adjacent to or in contact with detector 1704, transceiver1412 is enabled.

In another embodiment, if detector output signal 1706 does not indicatethat an object is positioned adjacent to or in contact with detector1704, transceiver 1412 generates RF communication signals while varyingits carrier frequency (i.e., performs frequency hopping) among aplurality of frequencies. If detector output signal 1706 does indicatethat an object is positioned adjacent to or in contact with detector1704, transceiver 1412 significantly reduce output power while hoppingor utilizes a single oscillator frequency as a carrier frequency forcommunication with the object (i.e., does not perform frequencyhopping), which may be a tag. In this manner, detector 1704 enables RFIDmodule 1702 to communicate with a nearby or contacted tag withoutfrequency hopping but at significantly reduced RF power levels. Asdescribes above, the communication can occur with a substantial amountof the output transmitter power of RFID module 1702 being conducted intothe tag, without radiating substantial power, enabling RFID module 1702to keep radiated power low enough so as to not be required to frequencyhop (according to local regulations, such as FCC regulations in theU.S.).

FIG. 18 shows a RFID communication system 1800, according to anotherexample embodiment of the present invention. As shown in FIG. 18, system1800 is configured generally similarly to system 1400 shown in FIG. 14,with a RFID module 1802 shown in place of RFID module 1402. RFID module1802 is generally similar to RFID module 1402, with the addition of adetector 1804 and a tuning module 1806. In an embodiment, detector 1804outputs a detector output signal 1810 to indicate that an object (suchas a tag) is positioned adjacent to or in contact with detector 1804.Detector output signal 1810 is received by tuning module 1806. Ifdetector output signal 1810 indicates that an object is positionedadjacent to or in contact with detector 1804, tuning module 1806generates a tuning signal 1812 to tune an antenna 1808 such that antenna1808 is efficient at radiating energy into the nearby object, and atreceiving energy from the nearby object. If detector output signal 1810indicates that an object is not positioned adjacent to or in contactwith detector 1804, tuning module 1806 does not generate tuning signal1812 to tune an antenna 1808. Thus, antenna 1808 may remain efficient atradiating communication signal into the far field region, if antenna1808 was originally configured as such.

In another embodiment, antenna 1808 may be configured to be self tuningfor efficient near field communications, and thus a separate tuningmodule 1806 and detector 1804 may not be required. For example, in anembodiment, antenna 1808 may be contacted with a tag. If antenna 1808 iscontacted with the tag, antenna 1808 is configured to be tuned by acapacitive loading of the RFID tag to radiate an RF signal receivable bythe RFID tag in the near field region. When antenna 1808 is not incontact with the RFID tag, antenna 1808 may remain efficient atradiating communication signal into the far field region.

FIG. 19 shows a RFID communication system 1900, according to anotherexample embodiment of the present invention. As shown in FIG. 19, system1900 is configured generally similarly to system 1500 shown in FIG. 15,with a RFID module 1902 shown in place of RFID module 1520. RFID module1902 is generally similar to RFID module 1520, with antenna system 1416including a first antenna 1906, a second antenna 1908, and a thirdantenna 1910. Furthermore, antenna interface 1414 is shown as an antennaselector 1904.

First, second, and third antennas 1906, 1908, and 1910 may be configuredin a variety of ways. For example, in an embodiment first antenna 1906may be a magnetic field sensitive antenna type, such as a loop antenna,suitable for near field region communications. Second antenna 1908 maybe an electric field sensitive antenna type, such as a dipole antenna,suitable for far field region communications. Third antenna 1910 may beconfigured for near field communications using an electric field, suchas for communications with a RFID tag that is adjacent to or in contactwith antenna 1910. In this manner, RFID module 1902 includes differenttypes of antennas for different communication environments. For example,although both first and third antennas 1906 and 1910 are suitable fornear field region communications, first antenna 1906 may be moreefficient at communicating through liquids such as water due to itsH-field sensitivity, and may communicate more efficiently with tags thatinclude loop antennas or other H-field sensitive antennas. Becausesecond antenna 1908 is an electric field sensitive antenna type, secondantenna 1908 may be more efficient at communications with tags thatinclude dipole antennas or other E-field sensitive antennas.

Antenna selector 1904 enables activation of one of antennas 1906, 1908,1910 for RF communications in a particular instance. Antenna selector1904 can electronically select one of antennas 1906, 1908, 1910according to a command from host computer 1402, according to a detectormodule similar to detectors 1604, 1704, or 1804, and/or by othermechanism, as would be understood by persons skilled in the relevantart(s) from the teachings herein.

Example Advantages of Embodiments

Numerous advantages are provided by embodiments of the presentinvention, some of which were described above. Example advantages aredescribed as follows that may or may not have been described above. Forexample, embodiments have a small size that is easy to integrate intomobile terminals. For example, ASIC and SAW devices can be integratedinto a laser scanner engine. Furthermore, the reader circuits can makeuse of existing laser scanner ASICs, such as being incorporated into thesame ASIC, or interfaced with the scanner ASIC in a convenient manner.The reader transceiver circuits use very low power. For example, thepower used is approximately the same as used by a laser scanner. Thereader embodiments are very light weight. Embodiments can be integratedinto a SANDISK™ (SD) format card to upgrade numerous existing productsand devices that are compatible with SD cards. Furthermore, due toreduced interference, embodiments allow more RFID terminal sales into agiven volume of space.

In a UHF reader embodiment, unlike other EPC UHF readers, thetransmitting frequency may be fixed (i.e., a single frequency), makingthe radio design very simple. The “fixed” transmit frequency does notnecessarily need to be centered at the resonant frequency of a tag. Forexample, a 2.4 GHz radio or 440 MHz radio may be used.

The reader antenna (e.g., antenna 422) may include an “inductive” coilpattern to operate at UHF frequencies or at 13 MHz for HF tags, and thetransmitter/receiver section, likewise, can include features for readingboth UHF and HF tags, such as a dual mode radio design.

A UHF antenna with very high Q can be used so as to be selective at adesired fixed frequency, as well as a low gain UHF antenna that isnormally part of a transmission line that only radiates when a tag is incontact to disturb the local field.

Embodiments can be implemented in a barcode scanner, that use a dualposition trigger of the scanner to select RFID or scanner operation.

A dip sensor can be used to remove the need for a trigger, with a powerstep feature for tag detection, and/or other proximity sensor conceptscan be used.

Carrier AGC (automatic gain control) can be used to improve S/N(signal-to-noise) as needed, so as to keep transmission power to aminimum, and to use power when needed.

Embodiments can be combined with continuous time signal processingtechniques, or other techniques, to simplify the transceiver circuitelectronics and to eliminate the need for a DSP (digital signalprocessor), and to produce DBP (digital barcode pattern) like signalsthat can be processed with today's low cost decoder CPUs, and/or share acommon baseband receiver and edge detector with a laser scanner, orlinear imager.

The transmit spectrum can be spread with simple techniques that takeadvantage of a coherent relationship produced in embodiments, therebyallowing more power on the transmit side while providing a securityfeature.

In embodiments, a baseband receiver with programmable filters and gaincan be used, an RF transmitter with programmable output power can beused, and/or an edge detector that can handle the signal and theinverted signal may be used.

As described above, embodiments can be packaged or implemented in SDcard format. Furthermore, embodiments can be packaged or implemented ina compact flash card, or packaged as an “RFID engine”. The RFID enginecould be used as a mobile computing accessory, a scanner “chin module”,or module mounted internal to the mobile device. The engine could useadapters (e.g., interface modules 1116, 1118, and 1120) to enable it tobe customized to each unique form factor.

Embodiments may be packaged on a rigid or flexible substrate, such asdescribed with respect to FIG. 12. For example, a flex substrate mayinclude an antenna strip (trace in flex). The flex substrate can beadhered to the inside contours of existing or new housings. Embodimentscan have multiple antenna strips supporting multiple frequencies, ifdesired. Antenna strips may be optimized for contact reading, as well asfor close range reading, such as 0 to 3″ or 0 to 6″ read ranges.

Embodiments for the reader engine can communicate with a host device(scanner, mobile computer, etc.) via conventional connector/contacts,via a personal area network (PAN) (e.g., BLUETOOTH), local area network(LAN) (e.g., 802.11), or other network. For example, embodiments mayutilize a PAN network so that it could be located/integrated onto hostdevices independent of existing accessory I/O connectors. It may houseit own independent power supply, or share a power supply, if desired

A motion sensor, such as a “MEMS” (micro-electromechanical system)motion sensor, may be present for enhanced power management. Forexample, a motion sensor may enable the device to go into sleep modewhen no motion is being detected.

Conventional systems tend to perform “far field” reads of tags.According to embodiments, as described above, a “near field” read can beperformed (or very short far field read). A space or region immediatelysurrounding an antenna in which reactive components predominate, isknown as the reactive near field region. The size of this region variesfor different antennas. For most antennas, however, the outer limit of anear field read is on the order of a few wavelengths or less. Beyond thereactive near field region, the “radiating field” predominates. Theradiating region is divided into two sub-regions, the “radiating nearfield” region and the “far field” region. In the radiating near fieldregion, the relative angular distribution of the field (the usualradiation pattern) is dependent on the distance from the antenna. In afar field region, the relative angular distribution of the field becomesindependent of the distance.

Example Computer System Embodiments

In this document, the terms “computer program medium” and “computerusable medium” are used to generally refer to media such as a removablestorage unit, a hard disk installed in hard disk drive, and signals(i.e., electronic, electromagnetic, optical, or other types of signalscapable of being received by a communications interface). These computerprogram products are means for providing software to a computer system.The invention, in an embodiment, is directed to such computer programproducts.

In an embodiment where aspects of the present invention are implementedusing software, the software may be stored in a computer program productand loaded into a computer system (e.g., a reader or host) using aremovable storage drive, hard drive, or communications interface. Thecontrol logic (software), when executed by a processor, causes theprocessor to perform the functions of the invention as described herein.

According to an example embodiment, a reader may executecomputer-readable instructions to read tags, as described above.Furthermore, in an embodiment, a tag may execute computer-readableinstructions to respond to a reader transmitted signal, as furtherdescribed elsewhere herein.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A radio frequency identification (RFID) system for communicating withRFID tags, comprising: a host computer; and an RFID module coupled tothe host computer, wherein the RFID module includes a transceiver, aprotocol processor configured to process RFID tag data, a host interfaceconnector module configured to communicate RFID tag data with thecomputer, a plurality of antennas, and an antenna selector to couple anantenna of the plurality of antennas to the transceiver.
 2. The RFIDsystem of claim 1, wherein the plurality of antennas includes: a firstantenna configured to receive a magnetic field component of anelectromagnetic wave; and a second antenna configured to receive anelectric field component of an electromagnetic wave.
 3. The RFID systemof claim 2, wherein the first antenna is a loop antenna.
 4. The RFIDsystem of claim 3, wherein the loop antenna is optimized for ultra highfrequency (UHF) frequencies.
 5. The RFID system of claim 2, wherein thesecond antenna is a dipole antenna.
 6. The RFID system of claim 1,wherein the plurality of antennas includes: an antenna configured to bemore efficient at radiating a communication signal into the near fieldregion than into the far field region.
 7. The RFID system of claim 3,wherein the antenna is a near field E-field coupling antenna, a nearfield H-field inductive coupling loop antenna, or a lossy transmissionline.
 8. The RFID system of claim 1, wherein the RFID module is anaccessory attached to the host computer.
 9. The RFID system of claim 1,wherein the host computer forms part of a barcode reader.
 10. A datacapture system for communicating with RFID tags, comprising: a hostcomputer; and an RFID module coupled to the host computer, wherein theRFID module includes a transceiver, a protocol processor configured toprocess RFID tag data, a host interface connector module configured toexchange tag data with the computer, an electronically configurableantenna system connected to the transceiver, and means to configure theantenna system to match properties of an antenna of a RFID tag proximateto the RFID module.
 11. The data capture system of claim 10, wherein theRFID module is an accessory attached to the host computer.
 12. The datacapture system of claim 10, wherein the host computer is part of abarcode reader.
 13. The data capture system of claim 10, wherein theelectronically configurable antenna system includes: an antennaconfigured to be more efficient at radiating a communication signal intothe near field region than into the far field region.
 14. The datacapture system of claim 13, wherein the antenna is a near field E-fieldcoupling antenna, a near field H-field inductive coupling loop antenna,or a lossy transmission line.
 15. The data capture system of claim 10,wherein the electronically configurable antenna system comprises aplurality of antennas.
 16. A radio frequency identification (RFID)reader, comprising: a transceiver; and an antenna coupled to thetransceiver; wherein in a first mode, the antenna is tuned to a firstfrequency; wherein in a second mode, the antenna is in contact with aRFID tag, wherein in the second mode, the antenna is configured to betuned for a second frequency different from the first frequency due to aload of the RFID tag in combination with a characteristic impedance ofthe antenna; wherein a radiation efficiency of the reader is optimizedfor the second frequency.
 17. The RFID reader of claim 16, wherein thetransceiver utilizes a fixed frequency for a carrier frequency.
 18. TheRFID reader of claim 16, wherein the transceiver is configured toperform frequency hopping.
 19. The RFID reader of claim 16, wherein inthe first mode, the antenna is configured to radiate a radio frequency(RF) signal having a first energy level, and in the second mode, theantenna is configured to radiate an RF signal having a second energylevel, wherein the first energy level is greater than the second energylevel.
 20. The RFID reader of claim 16, wherein an equivalentisotropically radiated power (EIRP) level radiated in the first mode isgreater than an EIRP level radiated in the second mode.
 21. A radiofrequency identification (RFID) device for communicating with RFID tags,comprising: an antenna configured to radiate a RF signal receivable byan RFID tag in a far field region; a transceiver coupled to the antenna;a proximity sensor that outputs a proximity signal indicating whetherthe antenna is proximate to an object; and a tuning module configured totune the antenna if the proximity signal indicates that the antenna isproximate to an object.
 22. The RFID device of claim 21, wherein iftuned by the tuning module, the antenna is configured to radiate anE-field radio frequency (RF) signal receivable by a RFID tag in a nearfield region.
 23. The RFID device of claim 21 wherein the antenna isconfigured to be tuned by contacting the antenna with a RFID tag. 24.The RFID device of claim 21, wherein an output power radiated by theantenna prior to being tuned is greater than an output power radiated bythe antenna when tuned.
 25. The RFID device of claim 21, wherein a powerlevel of an RF signal output by the transceiver to the antenna isreduced if the proximity signal indicates that the antenna is proximateto an object.